Hair Analysis Panel Discussion: Section 3.1
3.1 Sample Collection Methods
The panelists offered some varying opinions regarding the best way to collect samples. Topics discussed included preferred cutting tools, sampling location, and sample handling, as summarized below.
Selecting the appropriate cutting device. Panelists offered differing
views on what type of cutting tools should be used when collecting hair
samples. One panelist noted that metals can be released from scissors
and therefore recommended using quartz instruments (RB).
One panelist pointed out that if a stainless steel device is used, chromium and nickel results should be interpreted carefully, although he questioned whether use of stainless steel would really make a significant difference in the analytical results. This panelist questioned whether any data are available that document the extent to which chromium and nickel in stainless steel contribute to sample levels compared to quartz tools (MK).
In theory, said another panelist, labs that have used stainless steel scissors (for example) should run a careful blank for chromium. It is, however, difficult to do so: the variable concentration that is present in the specimen would be measured as well as the variable amount being introduced by the scissors. A chromium-free hair sample would be needed, which is not feasible (DP).
This same panelist stressed the importance of being sensitive to possible psychological and cultural issues when choosing a cutting tool. For example, children may be intimidated by certain types of shears or other cutting devices. Also, in certain cultures, hair is considered sacred. Touching, never mind cutting, is prohibited (DP).
One panelist suggested that if interferences due to the cutting instrument
used are proven to be significant, a new instrument might need to be created
that would be practical for field use (e.g., a relatively small tool with
a quartz blade) (LW).
Collection location. Because of differences in growth rates in
different regions of the scalp, the location from which a sample is taken
must be carefully considered to ensure consistency in measurements. For
example, the anterior and the parietal regions grow differently than the
vertex (top), occipital (back), and temporal (side) regions (RB). In response
to a question whether an optimal location exists, one panelist noted that
defining an optimal sampling protocol is difficult (DP). At a minimum,
it is important to choose a protocol that is practical in the field setting.
Another panelist noted the desire to identify a reproducible point on the skull. He suggested taking a sample from the nape of the neck (using a caliper to take the midpoint between the external auditory meatus), an area where hair is known to grow in a particular way (RB). Another panelist recommended sampling from the occipital region (SS).
In its 1989 study, CDC looked for a standard protocol but could not
find one. Therefore, CDC defined its protocol as follows: Approximately
500 to 1,000 milligrams of occipital hair was collected using stainless
steel scissors. Hair was pre-washed (using a non-ionic detergent). Samples
were stored in pre-cleaned plastic bags that were rigorously tested. Therefore,
within the context of the reference interval being generated, data were
from specimens collected in a like fashion (DP).
Sample storage. One panelist stated that plastic bags or other plasticware should not be used for storing hair samples unless the containers have been washed or cleaned. Zinc, he said, is used in plastic molding processes. Because detection limits are precise and relatively low, it is easy to record contamination from external sources; therefore, whatever container is used needs to be looked at with great scrutiny (RB)
Who should collect the sample. One panelist stressed that people not be allowed to collect their own samples, put them in plastic bags, and ship them off to the laboratory (MG). Others agreed: only trained professionals should collect hair samples.